In the oxygen-starved depths of the Pacific, a ghostly marine relic drifts in silence. The vampire squid (Vampyroteuthis

infernalis) is not quite a squid and certainly not a vampire, yet it may hold the clearest genetic clues yet to one of

evolution’s most complex transformations: how modern octopuses emerged from their squid-like ancestors.

A newly sequenced genome from this elusive cephalopod has unveiled a staggering discovery. At over 11 billion DNA base

pairs, the vampire squid’s genome is not only the largest ever sequenced in cephalopods, but also one of the most

anciently preserved. Hidden within this massive code lies a long-lost chromosomal blueprint—one that offers a rare

glimpse into the early genomic architecture of soft-bodied cephalopods and potentially explains the genetic leap that

gave rise to today’s octopuses.

The study, led by an international team of researchers from University of Vienna, Shimane University, and Japan’s

National Institute, positions the vampire squid as a unique genomic outlier: a slow-moving deep-sea scavenger that

quietly preserved the evolutionary past in its DNA for more than 180 million years.

An Oversized Genome Hiding in Plain Sight

The vampire squid’s genome—assembled using PacBio HiFi sequencing—revealed an unprecedented 11.2 gigabases of DNA, more

than four times the size of the human genome. Roughly 62 percent of this sequence consists of repetitive elements, a

feature that doesn’t produce proteins but may regulate how genes switch on and off.

This makes the genome both large and structurally informative. Researchers discovered that the vampire squid retained a

decapodiform-like chromosomal organization, resembling the arrangement seen in squids and cuttlefish. Despite belonging

to the octopod lineage, this genomic structure points to a shared evolutionary heritage that has remained largely

untouched.

“Its genome reveals deep evolutionary secrets on how two strikingly different lineages could emerge from a shared

ancestor,” said Oleg Simakov, a genomicist at the University of Vienna and co-lead author of the study published in

iScience.

In contrast, the octopus genome—roughly 2.7 billion base pairs—shows clear signs of large-scale chromosomal fusion and

rearrangement, evolutionary mechanisms that may have helped unlock more complex neural traits and adaptive behavior.

For a digestible overview of these results, ZME Science provides an excellent breakdown of the genomic sequencing and

its significance to evolutionary biology.

A Drifting Relic Between Squids and Octopuses

Despite its ominous name, Vampyroteuthis infernalis is a non-predatory deep-sea detritivore. It survives by feeding on

marine snow—a slow, continuous drift of organic debris in the deep ocean—and lives in oxygen-poor zones between 500 to

3,000 meters beneath the surface.

Its anatomy reflects this extreme niche. The vampire squid’s eyes, which can span up to 2.5 centimeters, are some of the

largest in proportion to body size in the animal kingdom, allowing it to detect faint bioluminescent flashes in total

darkness. Discover Wildlife offers a striking look at the vampire squid’s unique ocular adaptations and eerie footage of

its deep-sea behavior.

Although classified as an octopod, the species shares more in common—genetically and morphologically—with squids. It

remains the only living representative of the Vampyromorpha, a group of deep-sea cephalopods that has remained

genetically stable for millions of years.

The research confirms that the vampire squid retains features once shared by both major modern cephalopod groups,

bridging the evolutionary gap between Octopoda (octopuses) and Decapodiformes (squids and cuttlefish).

Ancient Architecture, Modern Insight

The genomic data highlights a major evolutionary shift: modern octopuses appear to have evolved from squid-like

ancestors by undergoing irreversible chromosomal fusion and genome rearrangement. These structural changes reshaped how

genes are regulated and may have contributed to the development of high intelligence, camouflage abilities, and flexible

arms.

Unlike the octopus genome, which reveals extensive chromosomal reorganization, the vampire squid’s DNA shows only

minimal divergence from ancestral patterns. This strongly suggests that its genome has remained nearly untouched for

hundreds of millions of years.

In evolutionary biology, such preservation is rare. Living fossils are often defined by anatomy, but in this case, the

vampire squid represents a genomic fossil, retaining the genetic configuration of a long-extinct ancestor. The research

team emphasized that the species’ low-energy lifestyle—combined with deep-sea isolation—likely shielded it from the

selective pressures that triggered rapid evolution in other cephalopods.

In addition, researchers sequenced the genome of Argonauta hians, a pelagic octopod known for producing a thin,

shell-like egg case. Its genome revealed further chromosome reductions, adding evidence to the trend that octopod

evolution involved significant genomic compaction and specialization.